Three-piece, wound-core golf balls with balata (trans-polyisoprene) covers are typically preferred by professional and low handicap amateur golfers. These balls provide a combination of distance, high spin rate, and control that is not available with other types of golf balls. However, balata is easily damaged in normal play, and thus lacks the durability required by the average golfer.
Two-piece golf balls, which are typically used by the average amateur golfer, provide a combination of durability and maximum distance that is not available with balata covered balls. These balls comprise a core, formed of a solid sphere which typically comprises a polybutadiene-based compound, encased in an ionomer cover, such as SURLYN.RTM.. Golf ball cover ionomers are, typically, copolymers of an olefin and an unsaturated carboxylic acid in which at least a portion of the carboxylic acid groups have been neutralized with a metal ion, typically sodium or zinc. These balls are extremely durable, have good shear resistance, and are difficult to cut. However, this durability results from the hardness of the ionomer, which gives such balls a very hard "feel" when struck, which many golfers find inferior to the softer "feel" of a balata covered ball. In addition, the hardness of the ionomer gives the balls a lower spin rate, making these balls more difficult to control.
Many attempts have been made to produce a golf ball with the control and feel of a wound balata ball, and the durability of an ionomer covered two-piece ball. These attempts have focused largely on modifying the properties of ionomer compositions by forming ionomer blends.
For example, U.S. Pat. Nos. 4,884,814, 5,120,791, 5,324,783, 5,415,937 and 5,492,972 disclose ball compositions which are blends of high-hardness ionomers and low-hardness ionomers. Other patents disclose blends of ionomers and nonionic polymers, such as U.S. Pat. Nos. 5,397,840, 5,516,847, 5,703,166. These patents attempt to overcome the inherent immiscibility of ionomers and nonionic polymers by adding polar functionalities to the nonionic polymers (see, e.g., U.S. Pat. Nos. 4,986,545 and 5,359,000), or by adding compatibilizers to provide or enhance the compatibility of the two polymer species (see, e.g., U.S. Pat. Nos. 5,155,157 and 5,321,089, and Japanese patent application 6,192,512 (1994)). Still other patents disclose blends of normally immiscible or poorly miscible non-ionomer polymers with compatibilizers (see, e.g., U.S. Pat. No. 5,422,398).
U.S. Pat. No. 4,526,375 discloses golf balls having improved low temperature impact resistance including a cover composition having an ionic polymer with at least two different metal ions in one molecule.
U.S. Pat. No. 5,692,974 discloses compositions using cationic polymers having positively charged quaternary ammonium groups. The cationic groups, preferably present in cationic polyurethane polymers, impart improved characteristics to golf ball covers formed therefrom.
Notwithstanding these efforts, there is no known prior art disclosure of the use of anionic polymers having anionic groups derived from other, non-carboxylic acid, neutralizable moieties, such as hydroxyl and dealkylable moieties, such as ether groups, to form golf balls. Such anionic polymers would have desirable hydrogen bonding or dipole interactions as well as ionic interactions which can be utilized to impart improved characteristics to golf ball cores, covers, and intermediate layers, such as improved durability and resiliency.
Thus, there has now been discovered surprisingly improved golf ball-forming compositions comprising anionic polymers having anionic moieties derived from neutralizable hydroxyl and/or dealkylable ether groups, which, when used to form golf balls, produce balls which unexpectedly remedy the deficiencies of the prior art materials discussed above.